1. Field of the Invention
The present invention relates to an ink-jet printing apparatus, in particular to an ink-jet printing apparatus that performs a printing process by discharging ink and a treatment solution or liquid for making dye stuff of the ink insoluble or coherent.
2. Description of the Prior Art
An ink-jet printing method has been widely applied in printers and the like because it has many advantages of quiet printing, less running costs, size reduction, and printing in colors, and so on, without great difficulty.
Previously, if an image is printed on a printing medium such as a piece of ordinary paper by the ink-jet printing method it often happens that the quality of the image declines in consequence of spreading ink on the paper, or the like. In general, ink to be used in the ink-jet printing method is mainly composed of water, so that the ink runs on the paper. In the case of printing a color image, in particular, several color inks are stacked one after another on the printing medium without intervals enough to fix each color. As a result, bleedings can occur on a boundary between the colors and it often lowers the quality of the image. Furthermore, there are some printed matters obtained by the ink-jet printing method where ink does not show sufficient water-proof characteristics.
To solve the above problems on the ink-jet printing method, for example, Japanese Patent Application Laying-open No. 128862/1983 discloses a technique of discharging a treatment solution having an effect of fixing recording ink on a recording medium so as to place them one on top of the other before or after discharging the recording ink. In this document, there is described the method of generating data for discharging the above treatment solution, in which the discharge data is provided as a result of performing a logical OR with respect to the discharge data of cyan, magenta, and yellow.
Japanese Patent Application Laying-open No. 63185/1989 also discloses a technique of improving a waterproof property of ink. In this document, when a recording ink is attached on a recording medium after attaching a chemical compound that makes dye stuff of ink insoluble, printing is performed after setting a dot of the insolublizing compound so as to have a larger diameter than that of the recording ink.
Furthermore, Japanese Patent Application Laying-open No. 202328/1993, disclosing the same kind of technology, includes a description of improving the property of waterproof and the stability of fixation by using:
a method of discharging treatment solution on a printing medium prior to the ink-jet, in which the treatment solution is responsible for fixing the recording ink well to provide a waterproof property thereof; PA1 a method of attaching the treatment solution on the recording medium by a roller coating; and PA1 a method of attaching the recording ink and the treatment solution on the recording medium after mixing them by an injection device during their flying in the air. PA1 a discharge data memory for storing a predetermined amount of discharge data for the ink-discharge portion; PA1 discharge data former for forming discharge data of the liquid based on the discharge data stored in the discharge data memory, an amount of the discharge data of the liquid formed being less than the predetermined amount of the discharge data stored in the discharge data memory; PA1 a liquid discharge buffer for storing the discharge data of the liquid formed by the discharge data former; and PA1 controller for driving the ink discharge portion to discharge ink and the liquid discharge portion to discharge the liquid according to the discharge data stored in the liquid discharge buffer and the discharge data memory, respectively. PA1 an ink discharge buffer for storing discharge data corresponding to a less amount of the discharge data than the predetermined amount for the ink-discharge portion; and PA1 a data-transfer switch circuit for switching a transmission of the discharge data stored in the discharge data memory to the discharge data former and the ink discharge buffer. PA1 a resolution converting circuit for converting a resolution of the discharge data to be transmitted to the ink-discharge buffer. PA1 a data-amplification circuit for increasing the amount of the discharge data formed by the discharge data former and transmitting the increased discharge data to the liquid discharge buffer. PA1 a plurality of discharge data memory portions for storing a predetermined amount of discharge data for the plurality of the color ink discharge heads, respectively; PA1 discharge data former for forming discharge for the liquid discharge head based on the predetermined amount of discharge data stored in the plurality of discharge data memory portions, the discharge data formed for the liquid discharge head corresponding to a less amount than the predetermined amount of the discharge data; PA1 a liquid discharge buffer for storing the discharge data for the liquid discharge portion formed by the discharge data former; PA1 a plurality of color ink discharge buffers for storing discharge data for each of the plurality of color ink discharge heads, respectively, each of the discharge data stored in the color ink discharge buffer corresponding to a less amount than the predetermined amount of the discharge data; PA1 a data-transfer switch for switching a transmission of the discharge data stored in the plurality of discharge data memory portions to the discharge data former and the respective plurality of the color ink discharge buffers; and PA1 controller for driving the at least one liquid discharge portion and the plurality of color ink discharge portions according to the discharge data stored in the liquid discharge buffer and the plurality of color ink discharge buffers, respectively.
As explained in the above three official documents, careful handling of the discharge data becomes a subject of the discussion in the technology of making the ink insoluble and flocculating dye stuff in the ink by discharging the treatment solution from a different head and mixing it with the ink. Among the above official documents, for example, Japanese Patent Application Laying-open No. 128862/1983 employs a logical OR of the discharge data of Y, M, and C as the way of generating data for discharging the treatment solution, as mentioned above. If a plurality of discharge orifices are formed on a head of each ink (typically this kind of construction is employed in most cases), the number of logical circuits and their incidental delay circuits and the like are required as much as the number of the orifices, causing a problem of constructing a comparatively complicated and large-scaled circuit structure. This problem is more serious in a printing apparatus using a so-called full line head.
To solve the above problem, for example, it is conceivable that discharge data of the treatment solution is previously formed for one line with respect to a scanning movement of the head and then the data of one line is stored in an exclusive memory from which the discharge data is read out every time the head discharges.
However, the memory has not been required when the treatment solution has not been used, thus resulting in a different problem of raising the cost of manufacturing the device. This problem becomes more remarkable in proportion to the amount of the discharge data depending on the number of orifices of the head and the extent of the printing area.